1. Field of the Invention
The present invention relates to a spherical orienting device, e.g., a two degree-of-freedom spherical orientation device driven via two actuation shafts, which supports an orientable device having an orientation axis, and the present invention further relates to a method for manufacturing such a spherical orienting device.
2. Description of Related Art
Two-dimensional spherical orienting devices, which orient an orientable payload device towards a desired direction in space by rotating it around a fixed point, are used in many fields of technology, for example in inertial sensors such as gyrometers, including in micromechanics, in gyroscopes, in orientable mirrors e.g. in two degree-of-freedom optical scanners, in gyroscopic stabilization of cameras and camera objectives, in water cannons for fire trucks or gaming, in robot wrists, artificial hands and in artillery equipment. Another important field of application is joysticks and similar input devices that sense the spherical orientation of an object rotated by a user, e.g. in user interfaces in automotive or industrial applications, in mobile hydraulic machinery, or in gaming or general computer user interfaces.
A conventional mechanism for the tilting of an orientable device into two directions is an assembly of two gimbals, i.e. pivoted supports that each allow the rotation of an object about a single axis, wherein one inner gimbal is mounted on an outer gimbal with pivot axes orthogonal or otherwise disposed at a non-collinear angle. However, in order to actuate the inner gimbal, an actuating motor or, in the case of an input device, rotational sensor has to be born by the outer gimbal. This leads to an increase of inertia for the outer gimbal, hindering fast movements, which are required in many applications.
In another conventional mechanism an orientable device is pressed onto a tip and tilted in two directions. The center of rotation is located at the apex of the tip where a bearing is installed. Due to such presence of material at the center of rotation, the object cannot be freely positioned within the mechanism, which is unsuitable for many applications. For example, in a case of the orientable device being a mirror such as in a mirror scanner application, the mechanism does not allow the mirror to be positioned such that the center of rotation lies in the mirror plane.
U.S. Pat. No. 5,966,991 discloses a two degree-of-freedom spherical orienting device in which a spherical five-bar mechanism with payload support is actuated by two rotary actuators fixed in position to a base. Payload support means for supporting a payload on an orientation axis include first and second revolute support joints each disposed for rotation about a support axis, wherein the orientation axis and each support axis pass through the spherical center of rotation in mutually orthogonal disposition. An inner sphere arm fixed to the shaft of the first rotary actuator is linked to the first revolute support joint of the payload support, the first actuator axis disposed orthogonal to the first support axis. A middle sphere arm is radially inwardly linked to the second revolute support joint of the payload support and outwardly linked to a middle revolute joint disposed for rotation about a linkage axis passing through the spherical center of rotation, the linkage axis disposed orthogonal to the second support axis. An outer sphere arm is fixed to the shaft of the second rotary actuator and linked to the middle revolute joint, the linkage axis disposed orthogonal to the second actuator axis.
Although the disclosed orienting device allows the payload to be positioned at the geometric center of rotation, the device requires a large spherical internal free space around the payload, independent of the shape of the payload to be oriented and of its orientation. Since in general applications orientable payload devices such as listed above are typically not spherically shaped, this leads to an undesirable large space requirement, in particular for orientable payload devices considerably deviating from a spherical shape, e.g. flat or elongate pay-loads. Large distances of the inner, outer, and middle sphere arms from the orientable device furthermore unfavorably influence high-speed operation due to an increased moment of inertia and the possibility of parasitic movements.
It is therefore desirable to provide a spherical orienting device that enables to orient non-spherical payload devices, in particular at high speed, without requiring a large installation space.